I agree with Ron. Sounds like your plugs are fouled. Look at them all, wet oily black carbon on them indicates oil fouling. This will happen if your engine uses some oil and never gets worked hard for long periods of time like when it was new and used for plowing. Fluffy black carbon on the plugs means too much fuel. Try leaning the carb a bit. The plug for this application if I'm not mistaken is Champion J-8. This is what should be used for heavy work. If you only use your tractor for light work or just riding around, try using a Champion CJ-14 or a J-19LM. These plugs are normally used in 2 cycle engines and are a hotter heat range to burn off oil. The suppression wires are only needed if you have or plan to use electronic ignition. Either way, start with a clean set of plugs. Hope this helps. Brian

The plugs I always used in my Allis B and WC back in the 50's were H-10's. Because of my oil burners, I switched to the hotter J-ll plug. I am not even sure if Champion makes these any more, but you should be able to find a cross reference in the parts stores. I believe these were the standard plugs to use in AC tractors.